1. Field of Invention
This invention relates to a bearing wheel body forming apparatus and particularly, to such an apparatus wherein the forming speed is controlled so as to result in more accurate concentric diameters of the wheel body.
2. Description of Prior Art
In forming a bearing wheel body comprising an inner circumferential surface, an outer circumferential surface and a body portion, a mandrel located next to a rotatable support roller is inserted into the wheel body while a wheel body forming roller is rotatably applied under pressure against the mandrel and the support roller so that the wheel body is rollingly formed into a desired shape for the inner circumferential surface, the outer circumferential surface and the body portion.
However, with the conventional wheel body forming apparatus, the wheel body has its width gradually thinned due to frictional wear during the rolling operation from initial rolling to final rolling. This results in such disadvantage as the wheel body having its circumferential moving speed changed gradually to a slow down state.
Also, if the speeds of forming roller and support roller are fixed, for example, being equal to each other, then circumferential speed of the wheel body is changed and becomes different from the circumferential speed of the forming roller. The result is that there occurs a "slip phenomenon" between the wheel body and the forming roller in order to offset the speed differential between the two. The "slip phenomenon" causes rotational irregularities to the wheel body which causes vibrations. Long term vibrations will cause the width of the wheel body to become thinned. In addition, the body may not be formed with a true circle which is a serious manufacturing defect.
Furthermore, the frictional wear of the wheel body forming roller is excessively increased due to the "slip phenomenon". This results in the disadvantage that the rollers must be replaced after only a short period of use, thus, reducing productivity and increasing costs.